Ok, let us say Jane Doe is raped. They do a rape kit, find DNA of her attacker. “OK, Jane, do you have any idea of who raped you?” (this is by no means a stupid questions, many rapes are by someone the victim knows). She doesnt. So, they run the DNA thru the criminal DNA database. No match.
Cops look for suspects, find none.
So, now, what do you do with the DNA evidence?
So if Jane has no idea to start, there is no big hurry. Still, that backlog is not a good idea, and it needs to be worked on.
Now, let us say Jane sez “Yeah, that halfback who got me drunk last nite”. Bingo, they have a suspect, they need to move NOW.